avcodec/x86: remove 3 sub in pred4x4_tm_vp8_8.

before:
  411 decicycles in ff_pred4x4_tm_vp8_8_ssse3, 8388289 runs, 319 skips

after:
  389 decicycles in ff_pred4x4_tm_vp8_8_ssse3, 8388308 runs, 300 skips

Tested on i7 920.
avcodec/old_codec_ids: fix missing FF_API_XVMC check

Signed-off-by: Michael Niedermayer <michaelni@gmx.at>
avfilter/vf_mp: fix missing FF_API_XVMC check

Signed-off-by: Michael Niedermayer <michaelni@gmx.at>